sling bag clip lock mechanism insert

I made this to solve an issue with "Sling Backpack Cross Body Shoulder Bag Messenger Daypack for Travel Gym School and Driving (Black)" from Amazon. The bag uses an open squared hook for connecting the strap to the bag on one end, presumably so you can easily take it on/off while - I don't know, wearing a seatbelt or parachute? Since nobody needs that feature, what ends up happening is the bag suddenly drops from your torso to the ground, to test the impact resistance of what's contained withi